Roof Moisture Surveys: An Effective Tool for the Industry

Roof Moisture Surveys:
An Effective Tool for the Industry

By Karl A. Schaack, P.E., BBC
When properly implemented, non-destructive
moisture surveys can provide a valuable bene¬
fit to all parties involved in the industry. The
main purpose of a moisture survey is to docu¬
ment the condition of the roof substrate materials (i.e.,
insulation board, absorptive decking material) or identify
the extent of moisture infiltration within a roof system.
Non-destructive moisture surveys can be performed
utilizing one or more of the following techniques:
infrared thermography, nuclear moisture meter technolo¬
gy, or capacitance moisture meter technology.
Infrared thermography basically identifies thermal
anomalies located on the roof. These thermal anomalies
are often associated with roof substrate materials which
have retained moisture. During warm weather, “wet”
substrate materials will retain a greater amount of heat
compared to adjacent “dry” materials. After the heat
source is removed (following sunset) and the surface of
the roof cools, infrared cameras can detect the “heated”
small roofs or
roofs clustered
with a significant
amount of roof¬
top equipment.
In addition, roof¬
top access is still
necessary in
order to verify
findings and
“questionable”
areas. With hand¬
held equipment,
basically every
square foot of
roof area can be
surveyed. Actual
boundaries or
delineation
Roof core confirmation of
construction and condition.
between “wet” and dry areas can be readily identified
wet substrate materials. During cold weather (winter
months), infrared cameras can detect interior heat that
and documented. The survey team personnel can iristan
taneously verify findings of the thermal scan. This level
transfers through the “wet” substrate materials due to
the reduced thermal resistance. Infrared thermography
can be accomplished utilizing hand-held equipment or
equipment that is mounted on aircraft. Aerial thermoof
survey is limited by the capacity of the survey team in
relation to site conditions. In addition, this type of sur¬
vey (whether hand-held or aerial) has to be performed at
night.
graphic surveys can provide a “quick” assessment of
numerous roofs or a large roof during a single night’s
survey time. However, these surveys have limitations on
The basis of the nuclear moisture meter relates to
recording the level or amount of hydrogen atoms located
within the roof system. A small
Suspected “wet” area delineated on the roof surface.
radioactive source within the meter
emits neutrons when the meter is
engaged. These neutrons react with
hydrogen atoms located within the roof
assembly and are backscattered. The
meter records the number of backscat¬
tered neutrons. The greater number of
backscattered neutrons recorded typi¬
cally indicates a larger presence of
hydrogen atoms, found in water.
Performing this type of survey involves
recording meter readings obtained on a
grid (5′ x 5′, 10′ x 10′) placed on the
roof surface. Once the readings are
obtained, a statistical analysis is per¬
formed of the readings in order to
6 • Interface March 1997
obtain suspected “wet”
and “dry” readings. Con¬
firmation of the condition
of the insulation (via
cores) at the various meter
readings is essential to
provide more precise data.
Upon determining the wet
and dry readings, the
quantity and extent of the
affected areas are extrapo¬
lated between the grid
points. This type of survey
is timely and can be per¬
formed at any time of the
day. The findings can be
considered “limited” as
the identified “wet” area
boundaries are based on
estimations and not actual findings.
The technology of a capacitance meter is based on
dielectric constants of materials. Most materials utilized in
roof construction have a much lower dielectric constant
than water. Therefore, as moisture within the substrate
materials is encountered, higher readings are recorded on
the meter. A grid survey similar to that utilized for a
nuclear gauge can be implemented. A mobile or rolling
model of the capacitance meter is available which can be
readily transported across smooth-surfaced roofs to survey
the entire roof area. If a grid-type survey is utilized, con¬
firmation of the roof components and extrapolation of the
findings are performed. A special model of capacitance
meter is manufactured to be utilized specifically on
EPDM roofs. This survey can be performed at any time,
with its major limitation being the presence of moisture
on the surface or within the membrane which may
“mask” the actual condition of the underlying materials.
These surveys can provide an added value to all those
involved in the roofing industry, from the contractor to
the architect to the building owner, during various phases
of the roof, including new construction, annual mainte¬
nance, and condition evaluation.
New Construction
A moisture survey can be beneficial in several facets
during the construction of a new roof. During construction/
roof installation, if water infiltration into the building
interior occurs or is suspected, a moisture survey can pro¬
vide an assessment of the actual moisture migration, if
any, that may have occurred. This survey can be very
beneficial in aiding respective parties in resolving dis¬
putes regarding actual damages. After completion of the
new roof, a moisture survey can be performed to docu¬
ment any possible areas of water infiltration that may
have occurred during work activities and to provide a
“baseline” of the condition of the roof substrate materials
for the start of its new “life.”
Roof Maintenance
After the roof is installed, roof moisture surveys can
become an added value to a routine maintenance pro¬
gram. When annual visual roof-top surveys are scheduled
and performed to assess the condition of a roof, a mois¬
ture survey can be an additional “tool” in the assessment
process. Whether the annual visual inspections are per¬
formed by a contractor, owner or independent third
party, roof moisture surveys benefit all.
When moisture surveys are performed early on and
throughout the life of a roof, small problematic areas that
may occur within a one-year time frame can be detected
rather than going undetected year after year.
Even if an annual maintenance program is not imple¬
mented, a moisture survey can be a valuable tool. If a
one-time assessment of the condition of the roof is per¬
formed, it becomes more critical to document the condi¬
tion of the substrate materials. Although a roof may
appear to be in relatively sound visual condition, under¬
lying “wet” materials could promote premature deterio¬
ration of the roof system components.
In conjunction with maintenance, moisture surveys
can also help contractors, building owners and others
make an accurate assessment of a roof that has sustained
physical damage due to severe weather incidents. For
example, if a roof sustains isolated physical damage (i.e.,
metal edge separation or lightning strike), the moisture
survey can identify if moisture has entered the roof sys¬
tem at the specific area and migrated.
Typical moisture meter test at core.
March 1997 Interface • 7
Repair/Replacement
Moisture surveys can also benefit an individual (con¬
tractor, architect, owner, etc.) when an assessment of the
condition of the roof is to be performed to determine
repair or replacement options. Prior to the preparation
and implementation of a repair scope of work, a moisture
survey can be performed. This survey can help in identi¬
fying problematic areas that otherwise may not have
been addressed in the repairs. In addition, if a signifi¬
cant amount of wet substrate materials is identified,
then it may not be cost-effective to spend the money on
repairs.
If the decision has been made that a new roof is
required, a moisture survey can be a benefit. If a new
recover roof system (existing roof remains) is being con¬
sidered, the moisture survey can identify areas contain¬
ing wet substrate materials which would need to be
removed and replaced prior to installation of the new
roof. If it is proposed that the existing roof be removed,
identification of areas retaining moisture can help in
quantifying anticipated repairs/replacement of deck
materials. Deck materials often become deteriorated or
non-salvageable when moisture is retained against the
respective material for an extended period. This identi¬
fication of wet areas can also assist the individual in
determining sequencing and/or appropriate materials to
be utilized during the roof replacement.
If a significant amount of water is encountered within
the roof assembly (which is common on structural con¬
crete decks), proper precautions should be made during
the roof removal process. Pumps, polyethylene sheeting
and other emergency types of equipment, tools, and
materials should be readily available when these areas
are encountered during the roof removal process.
Furthermore, if existing decking materials have been
subjected to extended periods of moisture, the decision
may be made to utilize different attachment methods
(mechanical attachment versus hot mopping/adhesive) or
different materials (venting base sheet versus glass base
sheet or fiberglass insulation versus fiberboard) for the
new roof assembly.
In summary, a non-destructive moisture survey can be
a valuable asset to all parties involved in the roofing
industry. Each technique has its specific limitations and
applications, and when properly implemented, can pro¬
vide the end user with important information to make
the appropriate assessment of existing conditions. Costs
associated with these surveys vary and could range from
$0.01 to $0.25 per square foot of roof area, depending on
the comprehensiveness of the scope of work and size
and configuration of the subject roof. Whatever the ini¬
tial cost of the survey, the resulting information could
provide exponential savings or, as a minimum, a direct
immediate return on the investment.
About The Author
Karl A. Schaack received a bach¬
elor of science degree in civil engi¬
neering from Clemson University
and is a professional engineer in
the states of South Carolina, North Carolina, and Texas.
He is Vice President of Houston Operations for Price ।
Consulting, Inc., and is a Registered Roof Consultant I
through RCI. ] ASBESTOS ANALYSIS
LEAD ANALYSIS
• AIHA AND AIHA ELLAP ACCREDITED
• 12 NVLAP ACCREDITED LABS
• 35 ELECTRON MICROSCOPES
• 160 EMPLOYEES
• AIR – DUST – BULK – SOIL – WATER – WIPE
• TEM – PLM – PCM – SEM – XRD – FAA – GFAA
• QUALITY ASBESTOS ANALYSIS SINCE 1981
CORPORATE OFFICE* MAIN LABORATORY
108 HADDON AVENUE, WESTMONT, NJ 08 108
1-800-220-3675
http://www.emsl.com
NEW YORK CITY – LONG ISLAND – PHILADELPHIA – GREENSBORO – ATLANTA
BUFFALO – DALLAS – HOUSTON • ANN ARBOR ■ SEATTLE • SAN FRANCISCO
Robert Stanford & Associates
Metal Roofing Consultants
• Scheduled Inspections During Construction
• Written & Photographic Reports
• Manufacturer Installation Certified
• Product Selection, Specifications
• Contract Document Preparation & Review
• Detail/Drawing Review & Recommendations
• Expert Witness Testimony
713.261.8522 … Fax 713.499.4840
4106 Waterstone Dr. • Missouri City, Texas 77459
Interested in advertising in Interfaced Just call 1-800-828-1902.
8 • Interface March 1997